Transmission of Xylella fastidiosa by naturally infected Philaenus spumarius (Hemiptera, Aphrophoridae) to different host plants

The recent establishment of Xylella fastidiosa subspecies pauca in the south-ern Italian region of Apulia threatens agricultural crops and the environ-ment. Olive is an important and widespread ancient crop in Italy and, sofar, the most impacted host. The meadow spittlebug Philaenus spumarius(Hemiptera, Aphrophoridae) has been identified as a vector of X. fastidiosain southern Italy; this species is one of the most common potential vectorsin Europe. To generate disease management strategies, data on X. fastid-iosa transmission by P. spumarius are necessary. Therefore, we carried outtransmission experiments by using field-collected spittlebugs in 2014 and2015 (5 and 11 collection dates, respectively), and transferring groups ofinsects immediately on to recipient plants. Various host plant species weretested: olive, oleander, sweet orange, grapevine and the stone fruit root-stock GF677 (Prunus persica 9 Prunus amygdalus). Xylella fastidiosa wasdetected in all the host plants after insect plant access except for grape-vine; infections to sweet orange and stone fruit were not systemic. In2015, estimates of insect X. fastidiosa infectivity were obtained; the num-ber of PCR-positive P. spumarius on each plant was positively correlatedwith the plant infection status. The proportion of P. spumarius infectedwith X. fastidiosa ranged from 25% to 71% during the entire survey per-iod. The number of X. fastidiosa cells detected in P. spumarius heads rangedfrom 3.5 9 10 to 4.0 9 102(CFU equivalents), which is lower than thatreported for leafhopper vectors in the Americas. These data show thatfield-collected P. spumarius have high rates of X. fastidiosa infection andare competent vectors.